Process for removing carbonyl compounds from hydrocarbons

ABSTRACT

Liquid hydrocarbons and mixtures thereof containing carbonyl compounds as impurities are purified by a liquid-liquid extraction with an aqeuous solution of a hydrazinium compound. The carbonyl free hydrocarbon phase is then separated from the aqueous phase.

United States Patent 1 1 Marx et a1.

[ Feb. 19, 1974 PROCESS FOR REMOVING CARBONYL COMPOUNDS FROMHYDROCARBONS [75] Inventors: Hans-Dieter Marx; Helrnut Scherb;

Bernhard Schleppinghoff, all of Dormagen, Germany [73] Assignee:Erdolchemie Qesellschatt mit bsEiEiiikir Haftung, Cologne Germany [22]Filed: Aug. 1, 1972 21 App]. No.2 277,021

[30] Foreign Application Priority Data Aug. 19, 1971 Germany 2141469 52us. Cl 208/289, 260/677 A, 208/48 AA, 260/680 R, 210/21, 260/6815 511111.01 C1 g 1, 00,97c 3 30 {58] Field of Search ..208/289,4A;260/677VA, 260/679, 681.5; 210/21 [56] References Cited UNITED STATESPATENTS 2,926,750 3/1960 Nelson 183/115 3,308,201 3/1967 Bowers et al260/677 A 2,966,455 12/1960 Stuart 208/254 Primary Examiner-Delbert E.Gantz Assistant Examiner-Juanita M. Nelson Attorney, Agent, orFirm-Ralph D. Dinklage [5 7 ABSTRACT Liquid hydrocarbons and mixturesthereof containing carbonyl compounds as impurities are purified by aliquid-liquid extraction with an aqeuous solution of a hydraziniumcompound. The carbonyl free hydrocarbon phase is then separated from theaqueous phase.

6 Claims, 2 Drawing Figures PATENIEB FEB 1 9 I974 SHEET 2 BF 2 PROCESSFOR REMOVING CARBONYL COMPOUNDS FROM HYDROCARBONS This invention relatesto a process for separating carbonyl compounds from hydrocarbons orhydrocarbon mixtures by treating the hydrocarbons or hydrocarbonmixtures in the liquid-liquid, two-phase system with an aqueous solutionof a hydrazinium compound and subsequently separating the carbonyl-freehydrocarbon phase from the aqueous phase.

The steam cracking of light petrols is accompanied by secondaryreactions which are evidently attributable to the chemical mixture alsocontains carbonyl compounds, especially aldehydes and ketones(hereinafter referred to as carbonyl compounds such as ethanal,propanal, acetone and others which, because of their boiling point,enter the C or C -fraction during separation of the cracking gases. Thecarbonyl content depends on whether the light petrol is cracked at loweror high temperatures. Normally the content varies within the range offrom a few hundred to more than 1,000 ppm, based on the hydrocarbons.Furthermore, carbonyl compounds can be fored in hydrocarbons asderivatives of compounds which are formed autoxidation of unsaturatedhydrocarbons.

Experience has shown that the carbonyl compounds have an inhibitingeffect during the further processing of otherwise pure hydrocarbons.Even quantities as small as 100 ppm have an extremely adverse effectupon stereo-specific polymerisation, especially in case whereorganometallic catalysts are used. In the hydrogenation of diolefms ordiolefin-containing mixtures, an increased carbonyl content contributestowards polymer fomration and deposition and hence towards deactivationof the catalyst.

The carbonyl compounds cannot be separated off by distillation becauseit is particularly the carbonyls of low molecular weight, such asethanal, propanal and acetone, which from azeotropes with numeroushydrocarbons, for example ethanol with 1,3-butadiene or acetone withisoprene, cyclopentadiene and piperylene, cf. Azeotropic Data, ACSMonography No. 6 Washington 1952.

Accordingly we have sought to find a process by which the carbonylcompounds could be removed in simple and economic manner fromhydrocarbons or hydrocarbon mixtures of the kind formed for exampleduring the working up of cracking gases.

SUMMARY We have now found that liquid hydrocarbons or hydrocarbonmixtures containing carbonyl compounds as impurities in quantities of upto about 5,000 ppm can be purified in a simple and economic manner bysubjecting the hydrocarbon or the hydrocarbon mixture to a liquid-liquidextraction with an aqueous solution of a hydrazinium compound andseparating the puriified hydrocarbon phase from the aqueous phase.

DESCRIPTION OF THE DRAWING The present invention will be more fullyunderstood from the accompanying drawing wherein:

FIG. 1 is a diagrammatic view of apparatus suitable for carying out theprocess of the invention continuously; and I FIG. 2 is a graph of fourcurves showing residual carbonyl content as described in Examples 2-5herein.

DESCRIPTION By the process of the invention, carbonyl impurities can beremoved from any hydrocarbon or hydrocarbon mixture which forms twoliquid phases with the aqueous hydrazinium compound solution under theconditions according to the invention, for example from saturated andunsaturated hydrocarbons, from the C and C -fraction which accumulateduring the cracking of light petrol, such as butadiene, butenespentanes, pentenes, isoamylenes, isoprene, piperylene, cyclopentadieneor from mixtures of these compounds.

Hydrazinium compounds suitable for use in the process according to theinvention include compounds of the general formula N I-I X (wherein X isa monovalent anion) which are soluble in water. Specific examples ofsuch hydrazinium compounds are hydrazinium sulphate, hydrazium chlorideand preferably hydrazinium hydroxide (hydrazine hydrate). Thehydrazinium compounds are used in an aqueous solution.

The molar ratio of the hydrazinium compound to the carbonyls shouldpreferably amount to at least 1 l, but more preferably to within therange 3 1 TO 10 l. The hydrazinium compounds are dissolved in water toform a 0.5 to 10 percent by weight solution and preferably a l to 5 byweight solution.

The extraction temperatures can be varied within a relatively widerange, the lower limit being determined by the freezing point of thewashing solution. The upper limit to the temperature range is imposedsolely by the requirement that two liquid phases should exist alongsideone another. In other words the temperature range rises with increasedpressure. In general, the reaction is carried out at a temperature inthe range of from 5 to 50C under a pressure of from 0.5 to 5 bars, andpreferably at a temperature of from 10 to 30C under normal pressure.

In the process according to the invention, a single wash with ahydrazine hydrate solution is sufficient to reduce the carbonyl contentfrom up to several thousand ppm to considerably below ppm, based on thehydrocarbon or the hydrocarbon mixture. In some cases, a simplesubsequent wash with water is required to remove traces of hydraziniumcompound dissolved in the hydrocarbons to below the detection limit.

The process according to the invention can be used for purifyinghydrocarbons by intensively contacting in a container a bath of thehydrocarbon or hydrocarbon mixture to be purified with the washingsolution and, thereafter, optionally washing the hydrocarbon phase withwater to remove traces of dissolved hydrazinium compound following phaseseparation.

In a preferred embodiment, the process is carried out continuously. Inthis case, any type of conventional mixer-separators can be used forintermixing the two liquid phases and for subsequently separating themagain. Following their separation, the hydrocarbons purified by theprocess according to the invention are washed with water and thenfurther processed. In a simple embodiment, washing with water can takethe form of, for example, a countercurrent wash. The continuousprocedure enables the hydrazinium compound in the washing solution to bemaintained in the required concentration to remove the carbonylcompounds by in the lower part of the mixing apparatus 6. Under theeffect of the mixing pump, the intensively mixed liquid streams from thefeed pipe 5 and the upper part of the mixing apparatus are guided intothe lateral pipe 11 of the mixing apparatus 6. The mixed phase flowsthrough the lateral pipe through a packed layer into the upper part ofthe mixing apparatus. From there, part of the mixed phase flows througha pipe 8 into a settling chamber 9, whilst the rest of the mixed phaseis drawn downwards into the mixing pump 7 back to the mixing zone.

The upper part of the settling chamber 9 is filled with a packing topromote phase separation. The purified hydrocarbon phase separated offis optionally washed by being delivered via a pipe 10 in countercurrentto a stream of water. The lower part of the settling chamber 9 acts as areservoir for the recycled aqueous solution of the hydrazinium compound.This solution is again delivered to the mixing apparatus through a pipe3 and can be replaced at any point by removing a fraction andintroducing fresh solution.

The process according to the invention has a number of advantages. Forexample, it enables reaction conditions such as temperature andpressure, under which the washing is carried out to be adapted toparticular requirements. The starting material can be directly subjectedto the process according to the invention in the liquid phase in aneconomically favourable manner. Another advantage is that the process ofthe invention functions without any loss of hydrocarbons because thehydrocarbons themselves do not react or are not prompted to react, forexample to polymerise, with the substances of the washing solution.

The process according to the invention is illustrated by the followingExamples:

EXAMPLE 1 Three-hundred ml of a hydrocarbon mixture of whichsubstantially'90% by weight consisted of cisand trans-1,3-pentadiene andsubstantially 10 percent by weight of other C -paraffins, -olefins,-diolefins and -acetylenes, was treated with aqueous hydraziniumhydroxide solution in accordance with Table l in a vessel mounted on avibration machine. The hydrocarbon mixture had an initial carbonylcontent of 2,100 ppm. The residual contents of carbonyl compounds in thehydrocarbon batches treated and the level of reduction (content ofcarbonyl compounds in the starting material/carbonyl compounds in thepurified mixture), are shown in Table 1. The contents of carbonylcompounds were determined with hydroxylamine hydrochloride in accordancewith an ASTM method, and are based on ethanal.

TABLE 1 Washing solution vibration residual reducttime content ionconcentration min. of carlevel ml/test of bonyl aqueous solutioncompounds of N l-1,011 ppm EXAMPLE 2 In an apparatus of the kind shownin FIG. 1, 1,000 ml/h of a hydrocarbon mixture with the same compositionas described in Example 1 (carbonyl content 2,100 ppm) were continuouslycombined through pipe 1 and pump 2 with 330 ml/h of an aqueous 5 percenthydrazinium hydroxide solution from pump 4 and pipe 3. The combinedstreams were delivered through pipe 5 into the mixing apparatus 6 andintensively admixed at substantially 2,000 rpm by means of a mixing pump7. The temperature was 20 C and the reaction took place at normalpressure. The mixed phase was delivered from the upper part of themixing apparatus through the pipe 8 into a settling chamber 9, the lowerpart of which acted as a reservoir for the washing solution. The clearhydrocarbon phase was run off from the upper part of the settlingchamber through pipe 10 and subjected to a countercurrent wash. Thehydrazinium hydroxide solution (1,300 ml in the system) was recycled.FIG. 2, curve 1 shows the residual carbonyl content in the hydrocarbonmixture in dependence upon the throughput. The hydrazinium compoundcontent of the purified hydrocarbon phase was below the detection limitof 1 ppm.

EXAMPLE 3 As in Example 2, 500 ml/h of a hydrocarbon mixture with thesame composition as in Example 1 (2,100 ppm of carbonyl compounds) weretreated with 425 ml/h of a 2 percent aqueous hydrazinium hydroxidesolution. The reaction conditions were the same as in Example 2. Theresidual carbonyl contents in the purified product are shown in FIG. 2,curve 2.

EXAMPLE 4 One thousand ml/h of the same hydrocarbon mixture as inExample 1, except that it had a carbonyl compound content of only 181ppm, were treated as in Example 2 with 330 ml/h of a 2 percent aqueoussolution of hydrazinium hydroxide. FIG. 2 curve 3 shows the residualcarbonyl content in the purified hydrocarbon mixture.

EXAMPLE 5 One thousand ml/h of a C -hydrocarbon fraction of the kindobtained during the cracking of light petrol which consisted of (inpercent by weight 30.9 percent of paraffins, 30.] percent of olefins,38.2 percent of diolefins and 0.7 percent of acetylenes, and whichcontained 1,242 ppm of carbonyl compounds was treated as in Example 2with 330 ml/h of a 2 percent aqueous hydrazinium hydroxide solutionunder normal pressure at a temperature of 20 C. Thereafter, the purifiedC fractions had a carbonyl content of only 50 60 ppm (see FIG. 2, curve4).

EXAMPLE 6 As in Example 2, 500 ml/h of 99.9 percent n-hexane which wascontaminated by 1,200 ppm of acetone, were combined and treated with 425ml/h of a 5 percent aqueous solution of hydrazinium hydroxide. It wasnot possible to detect any more acetone in the purified n-hexane by themethod of detection described in Example 1.

EXAMPLE 7 The process according to the invention was carried out in acontinuous countercurrent extraction installation (rotating-platessystem with an effective extraction zone of 3 metres) at a rotationalspeed of 520 rpm. 150 kg/h of a crude cyclopentene fraction consistingof 95 percent of cyclopentene, 3.2 percent of cyclopentane, l.8 percentof C -hydrocarbons and 423 ppm of carbonyl compounds, were guided incountercurrent to 30 kg/h of a 4 percent aqeuous solution of hydraziniumhydroxide. Extraction was carried out at room temperature and normalpressure, the washing solution being dispersed in the hydrocarbon phase.The purified crude cyclopentene thus obtained has a residual carbonylcontent of 18 ppm.

EXAMPLE 8 Seven hundred ml of a C -hydrocarbon fraction of the kindobtained during the cracking of light petrol, of which 4.9 percentconsisted of isoand n-butanes, 55.5

percent of isoand n-butenes, 38.9 percent of 1,3- butadiene, 0.7 percentof acetylenes and C -allene, and which had a carbonyl content of 88 ppm,was bubbled upwards through ml of a 0.85 percent aqueous hydraziniumhydroxide washing solution in a 300 ml capacity pressure vessel, at arate of 2,500 ml/h. To improve distribution, the hydrocarbon mixture wasforced through a glass frit at the base of the pressure vessel.Extraction took place at 20 under a pressure of 4 bars. The clearhydrocarbon phase was run off from the upper part of the pressure vesseland washed with water. The residual carbonyl content in the purified Chydrocarbon fraction, which was determined by the method described inExample 1, was below the detection limit of 1 ppm.

What is claimed is:

1. Process for purifiying liquid hydrocarbons containing aldehydes andketones as impurities in quantities of up to about 5,000 ppm. whichcomprises extracting said hydrocarbons with an aqueous solution of ahydrazinium compound having the formula N H X, wherein X is a monovalentanion, and separating the purified hydrocarbon phase.

2. Process of claim 1 wherein the hydrazinium compound is selected fromthe group of hydrazinium sulphate, hydrazinium chloride and hydrazinehydrate.

3. Process of claim 1 wherein from 0.5 to 10 percent by weight aqueoussolution of the hydrazinium com pound is used.

4. Process of claim 1 wherein the molar ratio of the hydraziniumcompound to the carbonyl impurities is within the range of 3:1 to 10:1.

5. Process of claim 1 wherein the extraction is carried out at atemperature in the range of 5 to 50C.

6. Process of claim 1 wherein the extraction is carried out at apressure of from 0.5 to 5 bars.

2 UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION a been: No.3,793IQ137 Dated February 19, 1974 Inventor) Hans-Dieter Marx et a1.

It is certified that error appears in the above-identified patent andthat said Letters Patent are'hereby corrected as shown below:

Column 1, line 14,after ",hemieal" insert --addi.tion 6"? water tohydrocarbons. Thus," the cra cking" "Column 1, linef'. after "comoounds"close parenthesi I Column 1, line2l "lower" should. read --low--;

Column 1, line 24 "fored" should read -formed--; Colmm 1, line 32 "case"should read v Y 7 L :--cases--; Column 1, line 36, "fomration" shouldread y --format;ion--; Column 2, line 25 "TO" should read v I v "to", rI

Signed and sealed this 19th day of November 1974.

(SEAL) At test: U

McCOY M. GIBSON JR. I c. MARSHALL 'DANN v Attesting Officer Commissionerof Pathts

2. Process of claim 1 wherein the hydrazinium compound is selected fromthe group of hydrazinium sulphate, hydrazinium chloride and hydrazinehydrate.
 3. Process of claim 1 wherein from 0.5 to 10 percent by weightaqueous solution of the hydrazinium compound is used.
 4. Process ofclaim 1 wherein the molar ratio of the hydrazinium compound to thecarbonyl impurities is within the range of 3:1 to 10:1.
 5. Process ofclaim 1 wherein the extraction is carried out at a temperature in therange of 5* to 50*C.
 6. Process of claim 1 wherein the extraction iscarried out at a pressure of from 0.5 to 5 bars.